Sister Madeline

"Sister Madeline" is the name Klaus gives the body of a nun when he tries to convince the family he has died in "No Weddings and a Funeral".

When the family is forced to gather together fifteen years after Klaus leaves due to not getting any respect by Sister Madeline, she insists they have a proper funeral for him. However, Sister Madeline is revealed to actually be Klaus, a fact that Roger quickly discovers. When the family still fails to say anything nice about him, Klaus knocks out everyone and places them inside of his fish body, where they are forced to work together in order to escape a fire that is accidentally set as they try to learn how to control him. After learning how to work together, and discovering that insulting Klaus has been the glue that holds them together, they reach the door but find they cannot reach the knob to escape the house, Klaus having buried it after using it to bury the nun he bludgeoned with it for her body. Klaus, appreciating that he actually is needed by the family. Together, the family manages to get Steve's pleasure bot to get them out of the house and they reunite as a family again.

She also appears during "Everyone is Happy in Utopia" in "300".

Sister Madeline is voiced by Dee Bradley Baker.